Method for assembling refractory metal rods in a heating system showing no overheated sections

ABSTRACT

A method of producing heating systems constituted by parallel rods of a refractory metal such as tungsten, tantalum or molybdenum, fitted at least at one end between cooperating connecting elements also of a refractory metal, to prevent the formation of overheated sections, ascribable to a faulty contact between the ends of the rods and the connecting elements. Between the assembled cooperating connecting elements is inserted a thin sheet of material such as copper or the like foil and is formed with the holes which are to receive the corresponding ends of the rods in the assembled elements and intermediate sheet. The thin sheet is then removed and the ends of the rods are fitted in the holes so that upon tightening of the elements over the rods, an intimate contact is obtained therebetween.

United States Patent nn 3 693 249 a a Monne Y 51 Sept. 26, 1972 [54] METHOD FOR ASSEMBLING 1,626,656 5/1927 Woodson ..l3/25 X REFRACTORY METAL RODS IN A 2,875,312 2/1959 Norton ..29/61 1 X HE TI SYSTEM SHOWING o 3,004,090 10/1961 Donovan et al. ..l3/25 OVERHEATED SECTIONS 3,395,241 7/1968 Roman ..13/25 [72] inventor: Maxime Monne, Paris, France primary p Campbe [73] Assignee: Sedimmec Societe dExploitation Exammervlctor D'Palma dlnventions Metallurgiques At'0mey Karl ROSS M h hi Fneclcizmques et C miques Paris ABSTRACT [22] Filed, Nbv 16 1970 A method of producing heating systems constituted by parallel rods of a refractory metal such as tungsten, [21] App]. No.: 89,990 tantalum or molybdenum, fitted at least at one end between cooperating connecting elements also of a refractory metal, to prevent the formation of over- [301 Foreign Apphcatmn Priority Dita heated sections, ascribable to a faulty contact between Nov. 14,1969 France ..6939328 the ends of the rods and the connecting elements.

Between the assembled cooperating connecting ele- 521 U.S.CI. ..29/6l1,13/25,219/552 ments. is inserted a thin Sheet of material Such as [51] Int. Cl. ..H05b 3/00 copper or the like foil and is formed with the holes 58 Field of Search ..29/611, 610; 219/523, 552; which are to receive the Corresponding ends of the 13/20 22 25 31 rods in the assembled elements and intermediate sheet. The thin sheet is then removed and the ends of [56] References Cited the rods are fitted in the holes so that upon tightening of the elements over the rods, an intimate contact is UNITED STATES PATENTS obtained therebetween.

1,574,108 2/1926 Peterson 13/25 2 Claims, 4 Drawing Figures |m mm i IME MONNE ATTORNEY METHOD FOR ASSEMELING REFRACTORY METAL RODS IN A HEATING SYSTEM SHOWING NO OVERHEATED SECTIONS FIELD OF THE INVENTION The present invention relates to the production of heating units.

BACKGROUND OF THE INVENTION The connection between a supply of energy and parallel rods of an electrical heating unit is a difficult matter since, when operative, the rods are raised to a high average temperature ranging between 2,300 and 2,800 C. A problem arises from the fact that, whereas this temperature is uniform throughout the operative length of the rods, the case is generally different at the points of contact between the rods and the elements connecting them with the electrical source. Such con necting points are readily overheated and the local temperature may rise substantially above 2,800 C., so that the metal is gradually vaporized. Consequently, the cross-section of the rods at these points decreases and its electrical resistance increases leading again to a further increase in the local temperature. After some time, the system becomes unserviceable.

OBJECT OF THE INVENTION My invention has now for its object a method for producing a heating system of the type referred to, which eliminates the risks of local superheating, so that premature damaging of the system is prevented.

SUMMARY OF THE INVENTION According to my invention, the two cooperating connecting elements between which the corresponding ends of the rods are to be clamped are firstly assembled with the interposition of a thin sheet such as a copper or a like metal foil, after which I drill within the thickness of the assembly obtained and across the thin sheet a plurality of holes or recesses, the diameter of which is substantially equal to that of the rods. The thin sheet being then removed, the rods are inserted in the holes thus formed and the connecting elements are tightly secured together, so as to firmly hold the rods in position.

DESCRIPTION OF THE DRAWING I have described hereinafter, by way of example and by no means in a limiting sense, an embodiment of my improved method, reference being made to the accompanying drawing wherein:

FIG. 1 illustrates a heating system produced in accordance with my invention, said figure being shown in elevational view on the left hand side and cross-section on the right hand side along I-I of FIG. 2.

FIG. 2 is a cross-section taken along line II-Il of FIG. 1.

FIG. 3 is a view from above.

FIG. 4 illustrates, on a larger scale, a detail of a pair of connecting elements during a stage of the execution of my improved method.

SPECIFIC DESCRIPTION As illustrated in the drawings, the heating system includes a plurality of parallel rods 1 made of a refractory metal such as tungsten, tantalum or molybdenum distributed along the generating lines of a circular cylinder, although the mode of their distribution is irrelevant and may be different. The rods are slightly spaced (angularly) with reference to one another and are interconnected at one end by connecting means designated generally by the reference number 2. At their opposite ends, the rods forming one half of the cylindrical system are connected with connecting means 3a while the rods forming the other half are connected with other connecting means 3b.

As illustrated more particularly in FIG. 2, the connecting means 2 includes two concentric radially slotted rings 4a and 4b made of molybdenum, tantalum or tungsten, the radial slot in the ring 4a being diametrically opposite to the radial slot in the ring 4b. The two rings are secured together by rivets illustrated diagrammatically at 5 and their contacting surfaces are provided with a plurality of cooperating substantially semicylindrical blind holes or recesses 6 within which the rods 1 are tightly held.

In order to produce such connecting means, I fit the ring 4b inside the ring 4a with the interposition of a thin sheet of copper foil 12 and I secure the two rings together by radial bolts 13 14 as illustrated in FIG. 4. I then produce the recesses 6 by drilling, the diameter of the recesses being substantially equal to that of the rod 1. The bolts l3-l4 and the copper foil 12 being then removed, I insert the rods in the recesses 6 and I interconnect the two rings 4a and 4b by rivets. By reason of the presence of a foil during the drilling of the recesses 6, the latter extend over an angle slightly less than on either side of the location of the rods 1 and, when the latter are inserted, this shifts slightly the rings radially away from each other. Thus the rivetting of the rings together causes the rods to be energetically clamped between the latter. The contact of each rod with the rings 4a and 4b extends continuously throughout the periphery of the rod clamped between the rings whereby local superheating is prevented.

Similarly, the connecting means 3a on one side of the rod structure may be constituted by a semi-circle of a metal such as molybdenum, tantalum or tungsten, which is secured by rivets 8 to the cooperating arcuate bent ends of two strips of refractory metal 9a and 9b. The rectilinear adjacent sections of the latter are furthermore secured together by rivets at 10 and are provided with holes 11 engaged by bolts securing them to energy-feeding electrodes. The connecting means 3b are executed in a manner similar to the connecting means 3a on the opposite side of the system.

Obviously, my invention is not limited to the embodi ment disclosed and illustrated and it includes all the modifications thereof falling within the scope of the accompanying claims:

What [claim is:

l. A method of producing a heating system including a plurality of parallel rods of a refractory metal and at least one pair of cooperating connecting elements clamping between them the ends of said rods facing a predetermined direction, said method comprising the steps of assembling the elements of each pair in sub stantially contacting confronting relationship with the interposition of a thin sheet, boring at spaced locations holes extending inparallelism with the desired location of the rods with reference to the elements, each of said holes being partly formed in both elements of the pair to either side of said thin sheet and having a diameter substantially equal to that of the rods, removing the thin sheet from between the assembled elements of a respective pair, fitting the ends of the rods in the holes l 

1. A method of producing a heating system including a plurality of parallel rods of a refractory metal and at least one pair of cooperating connecting elements clamping between them the ends of said rods facing a predetermined direction, said method comprising the steps of assembling the elements of each pair in substantially contacting confronting relationship with the interposition of a thin sheet, boring at spaced locations holes extending in parallelism with the desired location of the rods with reference to the elements, each of said holes being partly formed in both elements of the pair to either side of said thin sheet and having a diameter substantially equal to that of the rods, removing the thin sheet from Between the assembled elements of a respective pair, fitting the ends of the rods in the holes and securing the elements of the pair tightly together to clamp the rods between them.
 2. The method defined in claim 1, further comprising the steps of similarly boring holes in cooperating pairs of assembled further connecting elements and inserting the ends of the rods opposite the last mentioned ends in the holes bored in corresponding pairs of further connecting elements. 